In the processing of vinyl halide resins and more particularly polyvinyl chloride resins (hereafter PVC) to form moldable or extrudable compositions it is customary to incorporate into the polymeric resin, generally in dry powder form, a variety of additives for special purposes and to achieve the desired processing properties as well as the desired properties in the molded or extruded products. Among the additives generally employed are internal and external lubricants, pigments, heat and light stabilizers, fillers, antioxidants and the like. While the stabilizers generally employed are the liquid organo-tin compounds and while they can be added in liquid form the other additives are for the most part powders or granules. The normally solid additives can be added individually or as mixtures of such powders or granules and incorporated into the resinous polymeric powder in a mixer, typically a high shear mixer, in which the mechanical working of the material causes a rise in the temperature thereof and the additives become molten at temperatures of 100.degree. C. or higher and dispersed at the elevated temperature. For the most part, the normally liquid stabilizer is added to the polymer first and dispersed throughout the polymer at a relatively low temperature. Thereafter, the solid lubricants and waxes are generally added. Normally the lubricants generally include at least one wax that has a sufficiently low melting point to be melted in the mixer and become distributed on the surface of the polymeric powder. Then other additives may generally be added.
It should be recognized that such methodology is subject to a number of disadvantages and drawbacks. For example, numerous separate, time-consuming and error-prone weighings for each additives is required. Moreover, when masterbatching of additives is attempted the difference in physical properties of the various additives has led to inhomogeneity of mixtures thereof. Additionally, such mixtures tend to produce non-uniform agglomerations initially, on storage or when introduced into the mixing apparatus with the polymeric powder. Since some additives are used at low levels of about 0.1 part per hundred parts of resin, phr, this becomes a serious problem.
In attempts to avoid such problems it has been suggested to mix the solid paraffinic hydrocarbon wax, employed as the external lubricant, with the other solid additives, heat the mixture to an elevated temperature of 100.degree. C. or higher and thereafter cooling to recover a solid glass-like friable composition to be added to the polymer. However, this process still leads to an undesirable solid which has to be mixed with the polymeric powder along with all the problems that entails. Another less than satisfactory suggestion has been to form an aqueous emulsion of lubricants and stabilizers which is then mixed with solid additive to form a free-flowing additive concentrate powder. However, this process also results in an undesirable solid powder to be added to the polymeric powder. Also, attempts to add the additives in a molten state at elevated temperatures has been suggested but this has not really solved any of the problems.
It would be highly desirable to be able to incorporate all such additives as a liquid formulation. However, prior hereto no such acceptable method has been found. It is therefore an object of this invention to provide a liquid lubricating and stabilizing composition which is a liquid at normal ambient room temperature or a temperature of 50.degree. C. or less and thus substantially avoid or eliminate the problems associated with the mixing of solid additives to resin powders.
For the most part the industry has employed solid waxes, generally natural or synthetic hydrocarbon paraffin waxes having a melting point of 160.degree. F. or more, as one of the external lubricants necessary to provide the resin composition with improved processing properties, such as fusion time, mold release characteristics and the like. It has been suggested that low molecular weight mineral oils having a low viscosity in the range of about 100 to 150 SSU or less at 100.degree. F. can also be employed along with the solid paraffinic hydrocarbon waxes as an innocuous additional external lubricant. However, the industry has considered any substantial use of such mineral oil as an additional lubricant component to be generally undesirable except in quantities of no more than about 11/2% by weight based on the weight of resin. Use of amounts above this level have been considered unacceptable and undesirable and thus have been rigidly avoided since it was thought that the mineral oil was generally incompatible with the resin and amounts greater than this would lead to overlubrication and consequent diminution of both the processing properties of the resin composition and the properties of the products resulting therefrom. Thus, for these and other reasons only low molecular weight, low viscosity mineral oils in amounts of 1.5% by weight or less have been employed in rigid PVC compositions heretofore.